This invention relates to capacitive sensing circuit for process variables. As microstructure fabrication processes improve, capacitive sensors of process variables can be made in increasingly smaller sizes to reduce size and cost of products that include such capacitive sensors. As the size of capacitive sensors decrease, the rest capacitance is becoming increasingly smaller as well. Capacitive sensors with rest capacitances of about 15 pF, for example, can be constructed in layered sapphire structures, and without the use of dielectric oil to increase capacitance. With such small rest capacitances, stray capacitances that couple noise into the capacitive sensor become larger with respect to the rest capacitances. Signal-to-noise ratios are degraded, and noise becomes a significant part of total error in the sensor output. There is also increasing demand for improved accuracy in capacitive process sensors. As these demands increase, capacitive sensor non-linearity limits the error specifications of the sensor. A method and apparatus are needed to provide improved accuracy in capacitance sensors.